Research On Test System Of Dynamic Balancing Without Trial Weight With Initial Bow

In the rotating machine, the unbalance is the most common fault of the rotor.When the rotating shaft is balanced by the traditional balance method,the initial bending of the rotating shaft is always ignored.Initial bending is generated in the process of heat treatment and installation of the rotating shaft,which would cause vibration and more obvious for the slender shaft.Besides,concentrated lumped mass modals are adopted in most of the traditional finite element approach for modeling unbalances,which is not appropriate for the long slender rotors with unbalances distributed along the length of the rotor.But the continuous polynomial curve for eccentricity could be used to identify the distributed unbalance.So,it is a feasible method to introduce the eccentric curve in the modal balancing method for the balance of slender shaft.This paper introduced the initial bend theory firstly. The relationship between rotational speed with vibration caused by initial bending and eccentricity individually was determined after the analysis of the vibration mechanism of them.The best way of dynamic balancing is confirmed after the analysis of the effects of balancing process caused by different angle between initial bend and eccentricity and after the discussion of balancing way in the rotor with both,the best way is confirmed.Focusing on the problem of the eccentric curve of the rotating shaft in the traditional modal balancing method.we projecte the eccentric curveonto the xoz/yoz plane,then replaced them by three- order polynomial curve.For the estimation of the three- order eccentric curve,the equations of motion of the rotor system are introduced, which are used to estimate the three- order eccentric curve,emphasing on the damping of the rotor shaft.In addition, the calculation method which based on the rotor dynamics theory and the finite element method of the eccentric curve is introduced.Also the first order mode of rotor system is done.Finally the correction mass on the two planes are calculated based the modal balance formula.Based on the LabVIEW platform,a text system was developed,which including the rotor system dynamics modeling,the rotor system vibration testing, calculation of correction and so on.The developed system can used to test the rotor system, identification of the unbalance fault.The rotor vibration test analysis and online dynamic balance were carried out on the laboratory bench.The experimental results show the speed and the number of shaft segments have no influence on the accuracy of the eccentric curve, and proved that the vibration degree of the eccentric curve obtained by considering the damping of the shaft is greater,the balance effect is better.